Shane Todd worried that his employers in Singapore were using him to help China get its hands on sensitive technologies that could harm U.S. national security.

He said so to many folks, and was elated to have found another job back home, said his mother, Mary Todd. But two days after his final day of work in June and a going-away party with colleagues, his girlfriend found him dead, hanging from his bathroom door.

"We believe he was murdered," said Todd's father, Rick, an airline pilot who once flew for the U.S. military.

The Todd family has been pressing the U.S. government to look into what they say is a case of espionage and faked suicide to cover up their son's discovery that he may have been used to help China spy on his country. The circumstances of the death make no sense, they say, and the Singapore authorities have not been cooperative enough.

They have made little headway with U.S. authorities but on Friday the Todd family will meet Montana Democrat Sen. Max Baucus in Washington to make their case.

"We want a congressional investigation. We want to know how bad the damage is if" the technology his son was working with reached China, Rick Todd said.

Baucus said the U.S. government has not done enough to answer the Todds' questions, and that he doesn't know yet whether enough pressure has been put on authorities in Singapore to allow the FBI to assist in the investigation.

Shane Todd's family lived in California and Florida before moving to Montana. His dad had been a Navy pilot before becoming a commercial airline pilot.

Shane Todd was a wrestling standout and adept in his science classes. He graduated in 2005 with a degree in electrical engineering from the University of Florida, where he had many friends, his family said. He received his doctorate at the University of California-Santa Barbara. In 2010, he chose a job in Singapore because he was looking for adventure, he told his parents.

He went to work at the Institute of Microelectronics, a Singaporean government research institution, to work on cutting-edge technology involving powerful semiconductors. But an investigation by the Financial Times magazine found the technology has other applications desired by China, applications that can be used to disrupt enemy radar and communications.

Documents on a hard drive his parents found in his Singapore apartment included a draft agreement for IME to share what Todd was working on with Chinese telecommunications company Huawei, says Colin Humphreys, a pioneer in the emerging field of gallium nitride semiconductors. Huawei is known to U.S. intelligence agencies. Rep. Mike Rogers, chairman of the House Intelligence Committee, told CBS' 60 Minutes in October that the company has ties to China's military and intelligence services and is "a serious threat" to U.S. national security.

Humphreys, director of the University of Cambridge Center for Gallium Nitride, analyzed documents retrieved from Todd's hard drive at the request of the Financial Times. Speaking to USA TODAY, Humphreys said the documents show that Todd traveled for IME to the United States to be trained on equipment used to produce a powerful new class of semiconductors that outperform silicon and can be used to greatly boost the transmissions of cellphone towers, military radars and radar jamming devices.

Gallium nitride is most commonly used in LED lighting, to produce high-intensity light without much heat or energy use. The material is also used on wafers, similar to silicon chips in a computer, to power various electronic devices but with much greater efficiency and intensity. Todd was involved in cutting-edge research on using GaN wafers that were 8 inches in diameter and can be loaded with electronic devices. They are of the type used in the most advanced commercial and military land-based and airborne transmission equipment, Humphreys said.

The technology is "state of the art and developing and not many places in the world are at this point," he said.

The New Jersey-based company, Veeco, also gave Todd recipes for creating gallium nitride wafers to certain specifications, and planned to ship equipment to IME so it could produce gallium nitride wafers in Singapore, Humphreys said. Singapore is not restricted from receiving such "dual-use" technology, but China is, according to the Financial Times.

Huawei has denied "any cooperation" with IME on gallium nitride, and IME issued a statement denying that Todd was involved in classified work or anything connected to Huawei.

Mary Todd, however, told USA TODAY that the company's statement is at odds with what her son said to her in the months before his death. After returning to Singapore from his training with Veeco in early 2012, a new development caused him to become extremely anxious, she said.

"He told us he was meeting with a Chinese company that spoke in English to him and Madarin (Chinese) to the group," Mary Todd said. "He said 'I think I'm being asked to do things that compromise U.S. security and I'm very uncomfortable.'"

Mary Todd said from then on she and her son spoke every week. In conversations that lasted an hour or more, Shane's unease seemed to increase, she said.

"He said he'd been threatened, but he was very nebulous about it," Mary Todd said.

Todd was afraid he wouldn't find another job if he left before his contract was up. When he gave 60 days' notice, IME asked him to stay another 60 days to complete what he was working on. Todd agreed, his mother said.

"He said coming to Singapore was the worst mistake of his life," Mary Todd said. "He said he was extremely naïve. This was every conversation we had with him preceding his death."

Mary Todd asked her church to pray for her son, even though she thought it "sounded so far-fetched" that he was in real danger. "He was getting ready to come home. He had a ticket to come home."

On his last day of work, Shane Todd went out with friends to celebrate. It was June 22. Two days later, Mary Todd got a phone call that shattered her life. Shane's girlfriend called, hysterical, to say she found Shane dead. Police said it appeared Shane had killed himself.

Todd's parents were stunned, but their shock turned to confusion and anger after they traveled to Singapore.

The scene of his death didn't match the description police provided. Todd's body bore marks that an independent medical examiner later said looked as if he'd been in a fight and died by a garroting, or strangling. And evidence on a computer hard drive found in his apartment shows the work he was doing may indeed have been an illegal transfer of military-grade technology to a Chinese company that is known to have ties to China's military and intelligence services, the family said.

Despite the allegations, most U.S. government officials won't talk about the case.

The State Department declined to comment. Staffers for Sen. Jon Tester, D-Mont., helped arrange a meeting between the Todds and the U.S. ambassador to Singapore, according to Tester's spokesman, Dan Malessa.

Baucus has alerted top officials at the White House to the case and instructed staffers from the Senate Finance Committee, which he chairs, to raise the issue in face-to-face meetings with U.S. Embassy staffers and Singaporean officials, according to his office.

The family needs answers and there are national security concerns, Baucus told USA TODAY. "I will do everything in my power to help them get the answers they deserve," Baucus said.

Mary Todd said the FBI met with her and her husband once, in Singapore, "and we never heard from them again."

The FBI said it is talking to Singaporean authorities about assisting in the case.

The allegations of espionage and murder come as new developments arise over international spying. U.S. cybersecurity firm Mandiant issued a report in early February alleging widespread industrial espionage by the Chinese military against commercial entities across the United States. The Mandiant report is relevant to Shane Todd's case because it shows that "there is no clear line in China between commercial entities and China's military and government," said China expert Dean Cheng of the Heritage Foundation, a Washington think tank.

When Mary and Rick Todd arrived in Singapore on June 26, a police detective said their son hung himself with a wide strap from a computer bag, which he'd attached to a rope tied to the toilet and strung through a pulley he had bolted to the wall, Mary Todd said. The detective also read them an apologetic suicide note he said was found on Shane Todd's computer. The note started out thanking IME for the opportunity it offered and continued with apologies to the company and his family. She recalled thinking of the distinct tone of the letter that "it was so Asian."

"Then he gave this pathetic list of memories he had with our family that made no sense whatsoever," Mary Todd said. She handed the letter back to the detective and said her son "may have killed himself, but he didn't write this note."

The Todds' suspicions grew when they went to their son's apartment. There was no pulley and no bolts and no bolt holes, as the police report claimed. The toilet was not where the detective said it would be. There were clothes in the washing machine and piled on the couch in preparation to be packed. Furniture was tagged as if for sale. The apartment looked like someone was getting ready for a move to a new life, not end it all.

Edward Adelstein, chief pathologist at the Harry S. Truman Veterans Hospital in Columbia, Mich., and deputy medical examiner for Michigan's Boone and Callaway counties, disagreed with the preliminary official report that Shane Todd's death was a suicide. Adelstein noted thin marks on Shane Todd's throat, bruises on his forehead, neck and hands, and the normal weight of his lungs. Shane Todd died quickly and not without a struggle, Adelstein said.

Bruising on Todd's hands, neck and forehead were signs of a struggle, he said.

"Perhaps the most important information is that the deceased did not have a history indicating that he was considering taking his life, while there is significant history that he felt his life was being threatened," Adelstein wrote.

Rick Todd says he's not surprised his son tried to fight back.

"Shane was a very tough individual," he said. "He wrestled two years. He was extremely strong. He had a bruise on his forehead. He obviously was able to head-butt somebody."